methods for the euthanasia of dogs and cats- english.pdf

8/9/2019 Methods for the euthanasia of dogs and cats- English.pdf

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Methods or the euthanasiao dogs and cats: comparisonand recommendations

World Society or the Protection o Animals


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FOREWORD

This document aims to provide guidance on theeuthanasia o dogs and cats by identiying methodsconsidered humane and methods that might

compromise animal welare.

The euthanasia o companion animals is a muchdebated issue or animal welare organisations aroundthe world. Opinions are diverse and are oten inuencedby local situations and cultural backgrounds.

The decision to euthanase an animal is a complexethical matter involving many actors, and a detaileddiscussion o the subject is beyond the scope o this

document. As an animal welare organisation, it is ourobligation to ensure that when the decision to euthanaseis taken the methods used are truly humane andadministered by responsible and appropriately trainedindividuals.

Methods o euthanasia, scientifc knowledge andopinions evolve over time; this overview is based oncurrent scientifc evidence and will be subject to review.

Author: Louisa Tasker, MSc, BSc (Hons.)

Editor: Companion Animals Unit, World Society or the Protection o Animals

World Society or the Protection o Animals89 Albert Embankment

London SE1 7TP

T: +44 (0)20 7557 5000

F: + 44 (0)20 7703 0208

E: [email protected]

W: wspa-international.org


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CONTENTS

INTRODUCTION 4

Criteria or euthanasia 4

Reasons or euthanasia 4

Personnel and training 4

Signs o pain and distress 4Confrmation o death 5

Carcass disposal 5

Proessional and sympathetic conduct 5

METHODS FOR THE

EUTHANASIA OF

DOGS AND CATS 6

Summary table o methods:

Recommended 7

Acceptable 7

Conditionally acceptable 8Not acceptable 10

PRE-EUTHANASIA DRUGS 13

Tranquillisers 13

Sedatives 13

Immobilisers 13

Anaesthetics 14

Combinations o pre-euthanasia drugs 14

DISCUSSION OF

EUTHANASIA

METHODS 15

Non-inhalant, injectablepharmaceutical agents 15

Barbiturates 15Other intravenous anaesthetics 16

T61 16Potassium chloride (KCI) 16Magnesium sulphate (MgSO4) 17

Chloral hydrate (CH) 17Inhalant agents (gas mixtures) 17

General considerations 17

Anaesthetic gases 17Nitrogen or nitrogen/argon mixtures 18Carbon dioxide (CO2) 18

Carbon monoxide (CO) 19

Nitrous oxide (N20) 19Ether 19

Physical methods 20

General considerations 20Shooting using a ree bullet 20

Captive bolt 20Electrocution 20Decompression 20

Hanging 21Drowning 21

Poisons 21

General considerations 21Strychnine 21

Cyanide 21

REFERENCES 22

ANNEX 1:Dosages and routes o

administration o agents

or euthanasia o dogs and cats 23

ANNEX 2:Guidelines on the intravenous

injection o Pentobarbitone or

the euthanasia o dogs and cats 25


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INTRODUCTION

Criteria or euthanasia

The term euthanasia comes rom the Greek eumeaning good and thanatos meaning death, literallytranslated it means good death. There are our

primary criteria that ensure death caused by methodso euthanasia is humane (Beaver et al., 2001). Themethod must:

1 Be painless

2 Achieve rapid unconsciousness ollowed by death3 Minimise animal ear and distress4 Be reliable and irreversible

To meet these criteria, the method should take intoaccount the species, age and health o the animal. Inaddition the method should be simple to administer,sae or the operator, as aesthetically acceptable to the

operator as possible, and preerably require small doseso any chemicals used.

Reasons or euthanasia

A decision to euthanase an animal is a complex ethical

matter involving many actors, and a detailed discussiono the subject is beyond the scope o this document.The World Society or the Protection o Animals (WSPA)

believes euthanasia is acceptable and necessary whenan animal is suering due to an incurable illness orinjury, or when an animal presents a signicant risk to

human health and saety or the saety o other animals,through disease or aggressive behaviour.

It is advisable or WSPA member societies, which mayhave cause to euthanase animals in their care, to adoptan agreed euthanasia protocol that clearly outlines the

reasons or euthanasia and the acceptable methods.

WSPA does not condone the mass destruction odogs and cats as a population control measure.Successul control o dog and cat populations requiresa coordinated strategy that has been agreed by all

stakeholders and includes:

Legislation with eective enorcement Registration coupled with a dependable method o

identication or dogs and cats Reproduction control Measures to reduce the availability o dogs and cats

through the control o breeders, pet-shops and othersales outlets

Education o owners or guardians so that they act as

responsible carers or their animals

Even when these components are in place, WSPAreluctantly accepts that there are circumstances when

the euthanasia o healthy animals is required, orexample in the case o animals that cannot be rehomed,or to avoid overcrowding in shelters that wouldcompromise the welare o animals being held there.

WSPA rmly believes that in all situations wheneuthanasia is deemed necessary, the methods adopted

should meet all our o the criteria listed at the beginningo this introduction, and hence be truly humane.

Personnel and training

All methods o euthanasia have the potential to bepoorly perormed i operators are untrained andunsupported. Consequently, it is essential that

operators are provided with suitable training, includinga period o initial tuition with assessment o prociency,ollowed by continuous monitoring o skills and ability,

as well as access to emotional support.

The initial period o instruction should, without

exception, include training in both the technical aspectso the methods to be used and the recognition osigns o animal distress. Following the instruction,

operators should understand the mechanism bywhich that particular method o euthanasia causesunconsciousness and death. They should also receive

direction and practical training in the careul handlingrequired to prevent distress in the animals they will berestraining or euthanasia. It is essential that operators

are taught to recognise the species-typical behaviourand physiological responses that indicate an animal isexperiencing ear, distress, pain or anxiety, and how to

take immediate action to alleviate these states shouldthey be observed.

Signs o pain and distress

The ollowing behaviours or physiological responses

may be signs o pain and distress:

Aggression towards humans or redirected towards selor inanimate objects e.g. snapping, biting, growling,

scratchingVocalisation whining, whimpering, high pitchedbarking, howling, or growling in dogs, hissing or yowling

in catsAttempting to escape or withdraw rom the situationStruggling

Panting

Hyperventilating

Salivating


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Pupils becoming dilated

Pilo-erection (hair standing on end)Increased heart rate (tachycardia)Shivering, muscle tremors and spasms; these may alsoresult rom refex skeletal muscular contractionsImmobility or reezing (the animal becomes tense andstops moving, but remains conscious and aware o thesituation)UrinationDeecation

Anal sacs are emptied (oul smelling liquid isevacuated)

Confrmation o death

All operators perorming euthanasia should be able toidentiy when death has occurred. Indicators include:

Nomovementofthechest/Nosignsofrespiration

The animals chest has stopped moving up anddown indicating that it has stopped breathing.DO NOT rely on this sign alone as the animals

heart may continue to beat or some time ater it

has stopped breathing

Noheartbeat

Check or this with a stethoscope or by palpating

the animals chest wall.

Nopulse

Check or this by palpation over the medialaspect o the animals hind limb.Not always easy to locate in small animals

Lossofcolourfromthemucousmembranesinthe

animals mouth

Mucous membranes become pale and there is no

capillary rell i pressure is applied. With time themucous membrane becomes dry and sticky.Capillary refll is requently still evident or

prolonged periods ater an animal has died

Cornealreex(blinkreex)islost

The corneal refex is normally elicited when the

eyeball is touched. Ater death, the animals eyesremain open and the lids do not move when touched.

Glazingoftheeyes

This occurs rapidly ater death. The cornea loses its

clear, moist appearance and becomes opaque, dryand wrinkled.

Rigormortis

I death cannot be confrmed by a veterinary

surgeon, or there is any doubt, operators should

wait until rigor mortis has set in beore disposing o

the animals carcass.

Carcass disposal

Noanimalshouldbedisposedofuntildeathisveried

Disposalshouldtakeintoaccountregulations,

disease control and drug residues

Once death has been conrmed the animal shouldbe disposed o in accordance with the local and/ornational regulations. These rules should be obtained

rom the local municipality or relevant animal health/environment departments in advance and all operatorsshould comply with the necessary procedures.

This is especially important or disease control.Moreover, many o the injectable agents used oreuthanasia may leave residues in animal carcasses.

These drug residues may pose a threat to other

animals in the event that the carcass is eaten andmay cause localised contamination upon carcass

decomposition.

Suspectrabiescasesrequirecautioushandlingand

compliance with reporting regulations

Special precautions should be taken when handlingthe carcass o any animal suspected o carrying

rabies, including the use o protective clothing:gloves, overalls, eye goggles and protective shoes.

The carcass should be sealed in a plastic bag, asthe rabies virus can remain active or some timeater death. The external suraces o the carcass can

remain inective or several hours ater death, andthe internal organs can remain inective or severalweeks depending upon environmental temperature,

so burial is not recommended. National or localregulations may require that the carcass, head ora sample o brain tissue are sent to a public health

authority laboratory or testing and surveillance.

Proessional and sympathetic conduct

All operators need to show proessionalism and respector animal welare, or the value o animal lie, and

or other people involved. The degree o distress thatoperators and other people experience when euthanasia

is perormed will be aected by their culture, beliesand the community in which they live.

Operators should be emotionally supported and trained

to develop coping mechanisms to deal with this stress.This is important or many reasons, including the riskthat dissatised personnel may become careless whenhandling animals and performing euthanasia. Ensuring that

the methods used are humane can also help to reduce the

distress experienced by operators and other people.


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THEEUTHANASIAOFDOGSAND

CATS

The ollowing pages assess the methods o euthanasiain current use, in terms o the eects on the animal andadditional inormation regarding usage. The methods aredivided into the ollowing categories:

METHODS FOR THE EUTHANASIA

OF DOGS AND CATS

RECOMMENDED

This method is considered best practice because it

consistently produces a humane death when used asthe sole means o euthanasia.

ACCEPTABLE

These methods also produce a humane death whenused as the sole means o euthanasia. However, there

are practical limitations to their use.

CONDITIONALLYACCEPTABLE

These methods are acceptable only with caveats, dueto the nature o the technique, potential or operatorerror, or saety hazards to personnel. These methods

may not consistently cause death humanely.

NOTACCEPTABLE

These methods are inhumane and are not consideredacceptable or the euthanasia o dogs and cats.

Some methods o euthanasia can be used incombination with pre-euthanasia drugs, and these arediscussed ater the summary table. A detailed overview

o each euthanasia method, giving rationale or theircategorisation, is provided on pages 1521.


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RECOMMENDED

Method Remarks

Intravenous (IV) injection o 20%

Pentobarbitone solution

Barbiturate

Page 15

Regarded as best practice

Rapid acting

Rapid loss o consciousness, ollowed by cardiac arrest

May be used in combination with a pre-euthanasia drug i required or

earul, ractious or aggressive animals

No distressing side eects

Requires training

Relatively cheap

Not licensed or use in all countries

Cost and availability may vary rom country to country

Combinations o high concentrations o barbiturate with a local

anaesthetic may also be available and suitable i given intravenously as a

euthanasia agent

ACCEPTABLE

Method Remarks

Intraperitoneal (IP) injection o

20% Pentobarbitone solution

Barbiturate

Page 15

Slow acting

Takes longer to take eect than IV injection: 1530 minutes (dependent

upon the species and size o the animal)

A larger dose may be required than i given intravenously

May be used when collapsed or poor venous access precludes IV injection

May not be suitable or the euthanasia o larger animals

The use o pre-euthanasia drugs may prolong the time until death

May cause irritation to the peritoneum, particularly with

concentrations >20%

Can be combined with a local anaesthetic to reduce the risk o irritation

Animal may become distressed when it starts to lose consciousness

May be a practical alternative when IV injection is dicult e.g. or

ractious stray or eral cats, neonatal kittens and puppies. It is advisable to

return cats to a secure cage ater injection as they may become distressed

while the drug takes eect

Intravenous (IV) injection o

anaesthetic agents, given as an

overdose

e.g. Thiopentone or Propool;

Thiobarbiturate or Phenol

compound

Page 16

Rapid acting

Rapid loss o consciousness

May be suitable i animals are already anaesthetised or surgery and,

on humane grounds, not permitted to regain consciousness

Relatively large volumes or high concentrations required to euthanase

animals, potentially making it impractical or routine use depending upon

the commercial availability o the preparation

Under-dosing may lead to recovery

May be used in combination with a pre-euthanasia drug i required

Requires training

Cost may preclude routine use


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Method Remarks

Intracardiac (IC) injection o 20%

Pentobarbitone solution

Barbiturate

Only acceptable i animals are

anaesthetised by other means prior

to its administration (page 14)

Page 15

Rapid acting

Only suitable in collapsed, unconscious animals, or very young puppies

and kittens

May be suitable i animals are already anaesthetised or surgery and, on

humane grounds, not permitted to regain consciousness

Intracardiac route may be painul in ully conscious animals

Requires training, skill and knowledge o anatomy to ensure penetration o

the heart is successul on the rst attempt

Same licensing restrictions apply as with IV injection

Oral (PO) administration o

Pentobarbitone

Barbiturate

Only acceptable or neonatal

animals or to sedate animals prior

to intravenous injection o 20%

pentobarbitone solution

Page 15

Slow acting

Takes longer to take eect than IV injection (over 30 minutes)

May be suitable or neonates (within the rst ew hours/days o lie) aspoor venous access precludes IV injection

Not suitable or the euthanasia o larger/older animals

May be used to sedate animals prior to euthanasia with intravenous

injection o Pentobarbitone

Liquid orm o the drug may be detected by animals in their ood and

ingestion is avoided

Powdered orm may be delivered in gelatine tablets and hidden in ood to

encourage consumption

Animal may become distressed when it starts to become unconscious

Same licensing restrictions apply as with IV injection

Intravenous (IV) injection o T61

in a controlled manner, ater prior

sedation

Contains 3 drugs: general

anaesthetic, local anaesthetic and

curariorm-like agent


sedated by other means prior to its

administration and injection rate is

slow (page 13)

Page 16

Rapid acting

Causes death by respiratory collapse due to paralysis o the diaphragm

and intercostal muscles, resulting in asphyxiaRequires slow, steady rate o injection

Precise rate o injection is required: its use in ractious animals is

problematic

Intense pain may result i the injection is given too quickly, due to muscle

paralysis prior to loss o consciousness

It should never be used without prior sedation to permit slow rate o

injection

Requires training and skill

No longer available or use in the United States

Intravenous (IV) or intracardiac

(IC) injection o potassium chloride

(KCl) ater general anaesthesia

Concentrated electrolyte solution




Page 16

Rapid acting

Causes death by cardiac arrest

It should never be used without prior general anaesthesia to achievesucient insensibility and analgesia, to block the painul side eects o

this method

Requires training to ensure operator can assess suitability o anaesthetic

depth prior to use o KCl

Prior use o narcotic and analgesic mixtures adds signicantly to the cost

and prolongs the time o the procedure


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Method Remarks

Intravenous (IV) or intracardiac

(IC) injection o magnesium

sulphate (MgSO4) ater general

anaesthesia





Page 17

Rapid acting

Causes death by cardiac arrest

It should never be used without prior general anaesthesia to achieve

sucient insensibility and analgesia, to block the painul side eects

Requires training to ensure operator can assess suitability o anaesthetic

depth prior to its use

Large volumes are required or euthanasia

A saturated solution is required but this makes the liquid very viscous and

can result in diculty o administration

Prior use o narcotic and analgesic mixtures adds signicantly to the cost

and prolongs the time o the procedure

Inhalation o gaseous anaestheticssuch as halothane, enurane,

isourane and sevourane

Volatile inhalation anaesthetics

Page 17

Slow actingRequires high concentrations to be eective

Only suitable or small animals (weighing


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NOTACCEPTABLE

Method Remarks

Intravenous (IV) injection o T61

when used alone

Contains 3 drugs: general

anaesthetic, local anaesthetic and

curariorm-like agent

Page 16

May produce intense pain and causes death by paralysis o muscles

leading to asphyxiation prior to loss o consciousness i the injection rate

is too quick

Not acceptable when used alone or euthanasia

No longer available or use in United States


potassium chloride (KCl) given

alone or only with prior sedation


Page 16

Cardiotoxic causes cardiac arrest without rendering the animal

unconscious

Produces severe cardiac pain as a result

Sedation provides insucient analgesia to block painul side eects o

euthanasia agentNot acceptable when used alone or euthanasia


magnesium sulphate (MgSO4)

given alone or only with prior

sedation


Page 17

Causes cardiac arrest without rendering the animal unconscious

May cause intense pain and distress

Sedation provides insucient analgesia to block painul side eects o

euthanasia agent

Not acceptable when used alone or euthanasia

Oral (PO) or intravenous (IV)

administration o chloral hydrate

(CH)

Chemical reagent with sedative/

hypnotic properties

Page 17

Slow acting

Death results rom depression o the central nervous system resulting in

hypoxiaResults in convulsions, muscular contractions and gasping

Distressing and painul side eects

Large volumes are required to be eective

Not acceptable or euthanasia

Inhalation o nitrogen (N) or

nitrogen/argonmixtures

Gases

Page 18

Slow acting

Death due to hypoxia rom paralysis o the respiratory centre

Hypoxia may occur beore loss o consciousness even at high

concentrations, which is distressing or animals

Vocalisation, convulsions and tremors have been observed prior to death

Very young animals (


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NOTACCEPTABLE

Method Remarks

Inhalation o carbon monoxide

(CO)

Gas

Page 19

Slow acting

Highly variable time taken to lose consciousness and can take up to two

minutes at 6% concentration

Death by hypoxia

Vocalisations and agitation observed in dogs and this may occur while

they are still conscious

Distressing side eects observed in cats during induction

Animals


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NOTACCEPTABLE

Method Remarks

Electrocution

Physical method

Page 20

Although it is theoretically possible to apply a suitable current and voltage

across the skull (so that it passes through the animals brain) by trained

personnel using suitable electrodes, it is WSPAs experience that such

conditions are never achieved in practice

Whole body exposure to the electric current in an electrocution chamber is

not acceptable

Painul and inhumane under practical conditions

Dangerous to personnel

Not acceptable or euthanasia

Decompression

Physical method

Page 20

Slow acting

Death results rom hypoxia

Pain and distress results rom expanding trapped gases in the body prior

to the animal becoming unconsciousImmature animals are tolerant o hypoxia and require longer periods o

decompression beore respiration ceases

Aesthetically abhorrent as unconscious animals may bloat, bleed, vomit,

convulse, urinate and deecate during decompression

Totally unacceptable

Hanging

Physical method

Page 21

Death by asphyxiation rom strangulation

Causes ear and distress


Drowning

Physical method

Page 21

Slow acting

Prolonged death by asphyxiation caused by immersion in water

Causes ear and severe stressTotally unacceptable

Strychnine

Poison: Neuromuscular blocker

Page 21

Slow acting

Prolonged time or the animal to die and this can be highly variable rom

minutes to days depending upon the dose ingested

Causes violent and painul muscle contractions resulting in asphyxiation

Extreme danger to personnel


Cyanide

Poison

Page 21

Slow acting

Causes death by hypoxia and cardiac arrest

Results in violent convulsions and causes pain and distress while the

animal remains conscious

Extreme danger to personnel



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THANASIADRUGS

Pre-euthanasia drugs (tranquillisers, sedatives,

immobilisers or general anaesthetics) may be requiredto acilitate sae and humane handling o animalsprior to euthanasia, particularly i they are ractious,

aggressive or earul. Moreover, the prior administrationo suitable pre-euthanasia drugs may be necessary withsome conditionally acceptable euthanasia agents to

ensure they are humane.

The majority o these drugs require minimal animalhandling during their administration as they arepreerably given as a subcutaneous injection (unlesscontraindicated by the manuacturer), or sometimes as

an intramuscular injection or even via oral dosing. Theoperator then withdraws and waits or the drug to takeeect beore administering the euthanasia agent. Somepre-euthanasia agents, however, will require intravenous

administration. An important point is that the use othese drugs can add signicantly to the time taken toperorm euthanasia and this should be considered in

advance to saeguard animal welare.

There are several drugs that are commonly used prior to

euthanasia. It is essential that operators understand thedierent eects each o these has on an animal, as theiruse may not be appropriate or humane as an adjunct to

potentially distressing or painul euthanasia methods.Terms such as tranquillisation, sedation, immobilisationand anaesthesia describe the actions o these drugs.

These terms are sometimes incorrectly used as ithey were interchangeable, their specic meaning anddierent eects are explained below.

Tranquillisers

These drugs have some eects in decreasing ear andapprehension while the animal remains awake, making

it calm when exposed to low level stimuli. However,they have no analgesic eects and the animal is readilyaroused by painul stimulation. Oten they give a alsesense o security to someone handling an animal, which

appears calm but may then display enhanced and evenviolent responses to a strong stimulus such as a loudnoise or an approach by a person. This is potentially

dangerous to anyone who has to perorm euthanasia.

Example o common tranquillising agent:

Acepromazinemaleate(ACP) is a common tranquilliserused in animals, and has some depressing eects

on the central nervous system. Its principal use isin combination with other opiate drugs as a pre-

medication given beore anaesthesia. It will noteliminate any pain associated with euthanasia agents,and increasing the dosage above what is recommendedwill have little urther eect over the tranquillising

PRE-EUTHANASIA DRUGS

action, hence this drug cannot be recommended or sole

use prior to euthanasia with agents that may cause pain.Moreover ACP should not be used alone to calm earulanimals prior to euthanasia with any, even non-painul

agent, as it does not alter the animals perception o thesituation, merely its ability to respond.

Sedatives

These drugs depress the activity o the central nervous

system, resulting in drowsiness and muscle relaxation sothat animals become uncoordinated. I they are given insuciently high doses an animal may all into a sleep-likestate. However, they may not render the animal insensible

to pain: the animal generally remains conscious butcalm. As with tranquillisers, sedated animals can becomearoused by strong stimulation such as a painul procedure,

making their behaviour unpredictable.

Examples o common sedative agents:

Xylazine(Chanazine,Rompun,Virbaxyl,Xylacare)is a common sedative used with both large animals(equines and livestock) and small (companion) animals.

It induces muscle relaxation and also possesses someanalgesic properties. I used alone this drug may not bea suitable pre-euthanasia agent or some conditionally

acceptable euthanasia methods, as it does not inducesucient anaesthesia. In addition this drug will cause adrop in blood pressure, rendering subsequent intravenous

injection o euthanasia agents more dicult.

Medetomidine (Domitor) can induce sedation but must

be given in a suciently large dose. Its use also resultsin muscle relaxation and provides some analgesia. Aswith Xylazine, i used alone this drug may not be a

suitable pre-euthanasia agent or some conditionallyacceptable euthanasia methods, as it does not induce

sucient anaesthesia. Also as with Xylazine, thisdrug will cause a drop in blood pressure, renderingsubsequent intravenous injection o euthanasia agentsmore dicult.

Butorphanol (Torbugesic, Torbutrol) has some analgesicproperties. But both its sedative and analgesic eects

are dose dependent. However, this drug may not besuitable or sole use with some conditionally acceptableeuthanasia methods, as it does not induce sucientanaesthesia or analgesia. Its use is unlikely to produce

the drop in blood pressure caused by Xylazine orMedetomidine.

ImmobilisersThese drugs render the animal immobile by inducingparalysis. The animals body may become rigid and stiand the animal appears unresponsive to external stimuli


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THANASIADRUGS

such as sound. However, the animal can still eel painand thereore the sole use o immobilisers with painul,

conditionally acceptable euthanasia agents is notacceptable.

Example o common immobilising agent:

Ketamine (Ketaset, Vetalar) classed as a dissociativeanaesthetic, can also be used or restraint. It may

induce muscle rigidity when used alone and producesan altered state o consciousness (catatonia: not a losso consciousness). Unless combined with other drugs

such as Medetomidine, Xylazine and/or Butorphanol toproduce sucient analgesia and anaesthesia, it is notacceptable as a sole pre-euthanasia drug or use with

euthanasia agents that may cause pain. Injection byintramuscular or subcutaneous routes may be painul

and its rate o absorption can be altered.

Anaesthetics

These result in loss o consciousness and provide

good analgesia and muscle relaxation, so that surgicalprocedures can be undertaken.

Examples o common anaesthetic agents:

Tiletamine-Zolazepam(Telazol,Zoletil).This drugcombination oers good anaesthesia and allows or an

intracardiac injection o pentobarbitone or intravenousor intracardiac injection o conditionally acceptablemethods o euthanasia when properly administered.

This drug combination should be injectedintramuscularly.

Thiopentone and Propool. These drugs will result insucient anaesthesia to allow or intracardiac injectiono pentobarbitone or intravenous or intracardiac

injection o conditionally acceptable methods oeuthanasia. However, both o these drugs must be givenintravenously and may be unsuitable or use in animals

that are dicult to handle or restrain.

Combinations o pre-euthanasia drugs

Combinations o drugs may enhance their suitabilityas a prelude to euthanasia, especially i they possess

dierent, complementary analgesic and anaestheticproperties (e.g. Ketamine and Butorphanol). Suchcombinations should be chosen to render the animalinsensible to the pain that may result rom some

conditionally acceptable euthanasia methods. Whenusing a combination o drugs it is vital that a sucientdose o each drug is used, and that ample time is

allowed or them to reach their maximum eect beoreeuthanasia is undertaken. Moreover, animals should bemaintained in a quiet and calm environment as external

stimulation can prolong the time taken or drugs totake eect. Both o these actors can be aectedby an animals species (dog or cat), age, body size,

demeanour and metabolism, so the individual animals

drug requirements must be careully determined beorethis course o action.

Oral administration o drugs or combinations o drugsas a prelude to euthanasia has been explored or dogs(Ramsay and Wetzel, 1998) and cats (Wetzel and

Ramsay, 1998; Grove and Ramsay, 2000). For dogsa combination o Tiletamine-Zolazepam/Acepromazineor Pentobarbitone used alone consistently induced

sedation and lateral recumbency (Ramsay andWetzel, 1998). However, the time taken to produceproound sedation was prolonged (3090 minutes)

and highly variable between individuals.

In addition, the sole use o Pentobarbitone was

associated with struggling to stand and prolongedataxia during the onset o ull sedation. Theseundesirable eects were not observed or the

Tiletamine-Zolazepam/Acepromazine combination

and they may be ameliorated i Acepromazine isadded to the Pentobarbitone dose (Ramsay andWetzel, 1998), but this combination was not tested.

It is important to note that liquid preparations o thedrugs mixed with ood were detected and rejectedby dogs (Ramsay and Wetzel, 1998). Uptake by

dogs was greatly improved when the required doseo powdered preparations was placed in gelatinecapsules and hidden in canned (wet) ood.

The oral administration o Detomidine/Ketaminecombination was successul in sedating cats (Wetzel

and Ramsay, 1998; Grove and Ramsay, 2000)in comparison with other drugs tested (Ketamine,Detomidine, and Xylazine/Ketamine, Medetomidine/

Ketamine combinations). This particular combinationproduced reliable sedation within 1025 minuteso oral dosing (Grove and Ramsay, 2000). However

there are several undesirable side eects that maypreclude this rom routine use. The oral treatmento cats with all combinations tested (Detomidine/

Ketamine, Xylazine/Ketamine and Medetomidine/Ketamine) resulted in vomiting and excessivesalivation in some cats (Wetzel and Ramsay, 1998;

Grove and Ramsay, 2000) and is likely to causedistress to cats during induction prior to loss oconsciousness.

Food dosed with these types o drug is unpalatable,hence precluding accurate administration via ood.

However, the method o dosing used in these tests(squirting the liquid medicants directly into the catsmouth) is dicult to perorm remotely with any

accuracy. The handling o ractious or aggressive catsor oral dosing is likely to cause stress to the animals,thus presenting a welare issue as well as a potential

hazard or operators. Furthermore, Detomidine maynot be licensed or use in cats and guidelines or o-label use should be ollowed.


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The ollowing discussion provides greater detail

regarding the use and suitability o each methoddescribed in the summary table, to explain the reasonsor their categorisation. They are arranged by mode o

action and their acceptability or euthanasia.

Euthanasia agents are generally classied by their physical

characteristics: non-inhalant (injectable) pharmaceuticalagents; inhalant agents (gas mixtures); physical

methods; and poisons. They work by one o three modeso action (Close et al., 1996; Beaver et al., 2001):

Hypoxiadeathresultsfromreducingtheamountof

oxygen available to the animals cells and tissues.

Directdepressionofthenervecellsintherespiratory

centres o the brain necessary or maintaining lie

unction, leading to a loss o consciousness ollowedby death.

Physicaldisruptionofbrainactivitythrough

concussion, direct destruction o the brain, orelectrical depolarisation o nerve cells, leading to

rapid unconsciousness. Death occurs owing todestruction o the areas o the brain that controlcardiac and respiratory unctions.

Non-inhalant, injectable

pharmaceutical agentsBarbiturate, injectable anaesthetic agents,

T61, potassium chloride, magnesium sulphate

and chloral hydrate

RECOMMENDED

BarbituratesBarbiturates act by depressing the central nervoussystem, starting with the cerebral cortex, which

causes rapid loss o consciousness progressing toanaesthesia (Beaver et al., 2001). Their ecacy asanaesthetic agents ree rom distressing side eects iswidely recognised. With sucient dosages (overdose)

barbiturates induce respiratory and cardiac arrestby depressing the centres within the central nervoussystem that control these lie-maintaining unctions.

For euthanasia o dogs and cats, barbiturates thathave been specically ormulated as euthanasia

agents are preerred. The intravenous injection o 20%

Pentobarbitone solution is regarded as the most humanemethod o euthanasia or dogs and cats (Reilly, 1993;

Close et al., 1997; Beaver et al., 2001; European FoodSaety Authority, 2005) (see Annex 2). Dogs and catsare simply put to sleep; there is no audible or other

expression o pain. In some individuals a terminalgasp may occur when the animal is unconscious and

although this may distress some observers, it is not anexpression o pain or discomort, merely a refex action.Pentobarbitone is easy to use, relatively cheap and sae

or the operator (provided that it is not misused, e.g.deliberately sel-injected).

When the restraint necessary or giving an intravenous

injection would distress an animal or pose undue riskto the operator then prior sedation or anaesthesia

(pages 1314) or other accepted alternative routes oadministration should be employed (Beaver et al., 2001).

In an emergency situation the drug can be injecteddirectly into the peritoneal cavity (intraperitoneal).The time taken or the animal to lose consciousness

and die (1530 minutes) is longer than i the drug isgiven intravenously (a ew seconds). A higher doseo Pentobarbitone is required or intraperitoneal

euthanasia (Grier and Schaer, 1990; Sinclair, 2004)and it can cause irritation to the peritoneum, but thiscan be avoided i the drug is combined with a localanaesthetic.

There are no published reports on the use ointraperitoneal injection in dogs; nevertheless Sinclair

(2004) provides anecdotal accounts that dogsstruggle more than cats; repeatedly attempting toright themselves during the induction phase. For this

reason intraperitoneal injection may be unsuitable orlarger animals.

While most cats, kittens and puppies appear to advancemore smoothly to unconsciousness than adult dogs, theyshould be closely monitored, and conned to a warm,

dark, quiet place to acilitate distress-ree induction.The combination o Pentobarbitone and Phenytoin (acardiotoxic anticonvulsant drug) may be unsuitable

or intraperitoneal injection, because o concerns overthe dierential absorption rates o the two compounds(Sinclair, 2004). The eects o Phenytoin on the heart

may occur beore the Pentobarbitone component hascaused unconsciousness (Fakkema, 1999 cited bySinclair, 2004).

The technique or intrahepatic injection oPentobarbitone has been reported by Grier and

Schaer (1990). When correctly administered,its action is considerably aster in comparison to

injection via the intraperitoneal route, with cardiacstandstill being reported within 1114 minutes.However, perorming accurate intrahepatic injection istechnically dicult and may cause animals discomort

(Sinclair, 2004). Administration outside o the target

DISCUSSION OF

EUTHANASIA METHODS


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organ (the liver) is associated with excitement, whichmay also be distressing to the operator (Grier and

Schaer, 1990).

Injection o 20% Pentobarbitone directly into the heart

(intracardiac) may be suitable in collapsed, unconsciousanimals. However, this requires skill and knowledge oanatomy because ailure to inject into the correct place

will cause pain. It should only be used by experiencedtechnicians in an emergency.

It may be appropriate to administer liquid orm o a

suitable concentration o Pentobarbitone orally (bymouth) to neonatal puppies and kittens (within the rstew hours/days o lie) or euthanasia, as intravenous

access is dicult. The time taken or eect is longer

than i administered intravenously.

It should be noted that the time taken or oraladministration o Pentobarbitone to reach its maximumeect is prolonged (3090 minutes) and highly variable

between individuals given the same dose (Ramsay andWetzel, 1998). In addition to the lengthy inductiontime, other undesirable side eects may make this

method unsuitable or routine use, or instance somedogs may struggle prior to becoming ully sedated(Ramsay and Wetzel, 1998).

Oral administration o Pentobarbitone or euthanasiao juvenile or adult dogs and cats is unsuitable.

It may, however, be used to produce sedation orlight anaesthesia to precede intravenous injectiono Pentobarbitone or the euthanasia o ractious or

aggressive animals (Ramsay and Wetzel, 1998;Sinclair, 2004).

Some euthanasia products have been ormulated to usebarbiturates combined with a local anaesthetic agentor Phenytoin. The pharmacological dierences are

inconsequential when injected intravenously but suchcompounds may be more easily obtained insome countries.

WSPA considers the use o intravenous Pentobarbitoneor euthanasia o dogs and cats as best practice

(Annex 1, Annex 2) and its use is stronglyrecommended provided that it is legally permissibleand operators have been given appropriate training.However, suitable barbiturates are not always

available and in these circumstances WSPA urgesveterinary authorities, animal welare organisations andgovernments to strive to make these drugs legally and

easily available to the relevant proessionals.

ACCEPTABLE

Other intravenous anaesthetics

Other barbiturate drugs commonly used asanaesthetics, such as Thiopentone and newer agentssuch as Propool,will produce painless euthanasia igiven intravenously as overdoses (Annex 1). They work

in a similar manner to that described above, rapidly

inducing unconsciousness and death. However,larger volumes are required or euthanasia (Annex 1)and oten this makes their use more cost prohibitive

or routine euthanasia than Pentobarbitone. Inaddition these agents should not be given other thanintravenously, as they may cause tissue reactions at

the site o injection leading to pain and discomort. Aswith Pentobarbitone, they may be subject to restrictedlicensing practices.

ACCEPTABLEWITHCONDITIONS

T61

T61 is a mixture o three compounds (embutramide,

mebezonium iodine, tetracaine hydrochloride),which provide a combination o muscle paralysis

(via curarirom-like mechanisms), local anaestheticand general anaesthetic actions (Giorgi and Bertini,2000). The muscle paralysing agent rapidlyinduces respiratory collapse by paralysing the

animals diaphragm and intercostal muscles. Alocal anaesthetic acts to reduce (painul) tissueinfammation at the site o the injection, and the

general anaesthetic induces loss o consciousness.

The three compounds have dierent speeds o

absorption in the body (Beaver et al., 2001) andthere is a risk that i the injection is given too quicklythe animal will remain conscious during respiratory

collapse, which may produce pain (Giorgi and Bertini,2000) and distress (Hellebrekers et al., 1990) priorto death. For this reason T61 should be given by aslow and precise rate o intravenous injection (Beaveret al., 2001). This is likely to be dicult with animalsthat are anxious when being handled or restrained.

T61 should thereore only be used with prior sedation(page 13) to allow or close monitoring o injectionrate and to avoid causing pain to the animal. It should

never be given other than intravenously (Annex 1), asthe onset o action o each o the three constituentscan be altered when administered via alternative

routes (Beaver et al., 2001). T61 is no longer

available or use in the United States.


Potassium chloride (KCI)

The potassium ion is cardiotoxic (has a toxic eect

on the heart muscle) and rapid injection o potassiumchloride (KCI) as a saturated salt solution causescardiac arrest leading to death i given intravenouslyor by the intracardiac route o injection. It has no

anaesthetic or analgesic properties so i used aloneit causes animals intense pain prior to death. HenceKCI is only acceptable as the nal stage o euthanasia

in animals given prior narcotic or analgesic agents to

block its painul side eects (page 14). It is essentialthat personnel perorming this technique are trained

and knowledgeable in anaesthetic techniques. Theyshould be competent at assessing anaesthetic depthappropriate or subsequent administration o KCI.


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Euthanasia with KCl is only considered to be acceptablei animals are under general anaesthesia, characterised

by loss o consciousness, loss o response to unpleasant(including painul) stimuli and an absence o refexmuscle responses (Beaver et al., 2001). KCI can be

easily acquired, transported and mixed with water toorm an injectable, supersaturated solution (Annex1) to kill animals. However, the use o suitable pre-

euthanasia drugs will signicantly increase both thetime taken to perorm euthanasia and its cost.


Magnesium sulphate (MgSO4)

Magnesium sulphate (MgSO4) is a neuromuscularblocking agent. I delivered intravenously as a saturated

salt solution it will lead to cardiac and respiratory arrestollowed by death (Close et al., 1996). However, itcauses muscle paralysis (inducing respiratory arrest)without prior loss o consciousness (Beaver et al.,

2001); the animal thereore remains conscious butimmobile until the brain succumbs to lack o oxygen(European Food Saety Authority, 2005). Moreover

MgSO4 has no analgesic or anaesthetic propertiesto block the painul side eects and its sole use asan agent or euthanasia is inhumane (Close et al.,

1996, 1997; Beaver et al., 2001; European FoodSaety Authority, 2005). Dogs have been observed toexperience violent muscle spasms and contractions,

vocalising, gasping or breath and convulsion seizuresprior to death (Avariez and Caday, 1958), indicatingthat they experience pain and distress. As with

using KCI or euthanasia, MgSO4 is only acceptableas the nal stage o euthanasia in animals that areanaesthetised (page 14) and hence unconscious and

unresponsive to noxious (including painul) stimuli (andtheir refex muscle responses can no longer be evoked).Again, this requirement or pre-euthanasia drugs

signicantly adds to both the time taken to perormeuthanasia and to its cost. Furthermore, large volumeso MgSO4 are required (Annex 1) and an eective

saturated solution becomes very viscous and dicult tohandle or injection.

NOTACCEPTABLE

Chloral hydrate (CH)

Chloral hydrate (CH) acts slowly to depress the braincentres responsible or controlling respiration and

during the time taken to become unconscious animalsdisplay muscle spasms, gasp or breath and vocalise;indicating that they are in distress (Carding, 1977;Close et al., 1996). This drug has no anaesthetic or

analgesic properties to block the painul and distressingside eects and it is unacceptable or use in dogs andcats. Even with prior use o anaesthetics its slow mode

o action and the large volume required or it to be

eective make it unacceptable or euthanasia (Carding,1977; Beaver et al., 2001).

Inhalant agents (gas mixtures)

Anaestheticgases,nitrogen/argon,carbondioxide,

carbon monoxide, nitrous oxide and ether

General considerations

Inhalation agents used or euthanasia include volatileliquid anaesthetics and gases or gas mixtures that resultin hypoxia; delivered at increasing concentrations they

displace oxygen in the air breathed by animals (inspiredair) thereby lowering the concentration o oxygenreaching the lungs and tissues (Close et al., 1996).

To be eective, inhaled agents must reach a certain(minimum) concentration in the animals lungs (Beaver et

al., 2001). This means they do not induce an immediateloss o consciousness, and death ollows at some

considerable time later (European Food Saety Authority,2005). The humane induction o unconsciousness is

important, and any inhalation agents used must notbe unpleasant or the animal to breathe or producepain or distress prior to loss o consciousness (Closeet al., 1996, 1997; Leach et al., 2004; European FoodSaety Authority, 2005). In particular, inhalation agentsthat produce convulsions prior to unconsciousness are

unacceptable or euthanasia and should not be used(Close et al., 1996; Beaver et al., 2001).

Very young animals are particularly resistant to theeects o lowered oxygen concentrations (hypoxia/anoxia) because their haemoglobin (the oxygen-

transporting molecule in red blood cells) has a higheranity or oxygen than that o adults (Pritchett et al.,2005 cited by European Food Saety Authority, 2005);

an adaptation to being in the uterus. Young animals,thereore, take longer to die rom hypoxia than adults(Close et al., 1996; Beaver et al., 2001).

Inhaled agents may take longer to build up in the lungsand be eective in animals that are ill, injured or old, as

these animals may show decreased ventilation (shallowbreathing), making agitation more likely beore loss oconsciousness (Beaver et al., 2001).

In addition to these general considerations or animalwelare, the health and saety o operators is a major

concern with some o these methods. Both acute andchronic exposure to these agents can have toxic eectson humans (National Institute or Occupational Saety

and Health, 1977).


Anaesthetic gases

Halothane, Enfurane, Isofurane and Sevofurane arecommonly used as anaesthetic agents and can be

used or euthanasia i they are given as an overdose(Annex 1) (European Food Saety Authority, 2005).

However, these agents dier in the speed at whichthey induce unconsciousness and they possessvarying degrees o pungency, which animals may ndunpleasant (Leach et al., 2004; European Food Saety


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Authority, 2005). In addition, animals may struggle andbecome anxious during induction (Beaver et al., 2001)

because anaesthetic vapours may be irritating (Leach et

al., 2004). They are thereore not generally consideredto be suitable as sole agents or euthanasia in larger

animals (>7kg). Halothane is preerred because it maybe less aversive during induction (Leach et al., 2004)and produces anaesthesia more rapidly than the other

agents (Beaver et al., 2001; European Food SaetyAuthority, 2005).

Inhalation anaesthetic agents are vaporised and

delivered into chambers, via a ace mask or tube romanaesthetic machines; they are combined with air/oxygen during induction to prevent hypoxia (Closeet al., 1996, Beaver et al., 2001). The liquid states

o these agents are highly irritant, and animalsshould only be exposed to vapours. Chambers and

anaesthetic machines should be properly designed toensure that the gas is evenly distributed and that theanimal is rapidly exposed to eective concentrations

o the agent (Close et al.,1996). It is important touse equipment that is well maintained and to havescavenging units (devices used to reduce the pollution

in the air) to prevent personnel being exposed to theanaesthetic agents, as exposure to trace concentrationso anaesthetic gases is recognised as a human health

hazard (National Institute or Occupational Saety andHealth, 1977).

The large doses required or euthanasia are expensiveand tend to make this method cost prohibitive. Withthe diculty in administration and human health

aspects, this means that although this can be anacceptable method o euthanasia or small dogs andcats there are more suitable methods available (Closeet al., 1997; Beaver et al., 2001). The greatest valueo anaesthetic gases may be or the euthanasia o smallanimals (


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beore unconsciousness (Danneman et al., 1997; Leachet al., 2004). The cumulative stress associated with the

induction o unconsciousness when using CO2 is a seriouswelare concern (European Food Saety Authority, 2005).WSPA thereore considers this to be an unacceptable

method or the euthanasia o dogs and cats.

NOTACCEPTABLE

Carbon monoxide (CO)

Methods o generating carbon monoxide (CO) gas

or euthanasia o animals have included chemicalinteraction arising rom combining sulphuric acidand sodium ormate and the use o exhaust umes

produced rom idling petrol engines (Carding, 1977).Both o these techniques produce irritants that are

likely to result in considerable distress to animals andare thereore detrimental to the welare o dogs andcats (Carding, 1968, 1977; Close et al., 1996; Beaveret al., 2001), and hence their use is not acceptable.

Commercially compressed CO delivered rom cylindersinto specially constructed chambers has been used orthe mass euthanasia o dogs and cats.

CO combines with haemoglobin in the red bloodcells, decreasing the oxygen carrying capacity o theanimals blood. As a result, less oxygen is delivered

to the tissues and cells (hypoxia), which leads tounconsciousness, ollowed by death (Chaliouxand Dallaire, 1983). Although the animal becomes

unconscious within 12 minutes (variable betweenindividuals), death as conrmed by cessation oheartbeat does not occur until 1020 minutes ater

initial exposure to CO at concentrations reaching6% (Moreland, 1974; Chalioux and Dallaire, 1983;Dallaire and Chalioux, 1985). Although the welare

aspects o this method have not been well researched,a ew studies have reported that prior to loss oconsciousness dogs show signs o anxiety, including

moaning vocalisations (Carding, 1968; Chalioux andDallaire, 1983; Dallaire and Chalioux, 1985) andsigns o agitation (Moreland, 1974; Chalioux and

Dallaire, 1983). Furthermore, there is some concern

that the onset o convulsions (Close et al., 1996) andmuscular spasms (Moreland, 1974) may precede loss

o consciousness (Chalioux and Dallaire, 1983; Close

et al., 1997). Equally distressing behaviours have beenobserved in cats during the initial phase o euthanasia

using this method (Simonsen et al., 1981).

Use o the tranquiliser ACP prior to euthanasia with

CO signicantly reduced some o the behavioural andphysiological responses o dogs, but sucient timemust be allowed or ACP to reach its maximum eect

beore exposure to CO (Dallaire and Chalioux, 1985).

In addition to the risks or animal welare, CO is

extremely hazardous or humans because it is highlytoxic and dicult to detect. Even chronic low levelexposure is considered a human health hazard and isassociated with cardiovascular disease (Beaver et al.,

2001).

There are several practical limitations associated withthis method o euthanasia. Firstly, the construction,

diligent maintenance and careul operation o specialchambers are essential to reduce the risk to humanand animal welare; and these are likely to be costly.

Secondly, use o CO to euthanase certain groups oanimals is considered unacceptable (Humane Societyo the United States, undated). In particular, animals

under our months old (resistant to hypoxia); thosewith impaired breathing and or low blood pressure(due to systemic disease, injury or old age) will take

longer to succumb, causing additional distress priorto death. Use o CO inhalation to euthanase obviouslypregnant animals is also discouraged as the unborn

young will not be exposed to the gas and will die slowlyas a result o suocation, due to death o the mother

(Humane Society o the United States, undated).Moreover, unconscious dogs urinate, deecate andregurgitate (Moreland, 1974) making this aestheticallyobjectionable or operators and requiring chambers to

be thoroughly cleaned, adding to the time o use.

Although considered a conditionally acceptable method

o euthanasia by the American Veterinary MedicineAssociation (Beaver et al., 2001) and the HumaneSociety o the United States or some dogs and cats,

the many limitations o CO may make this method lesspractical, considerably slower and more expensive thanlethal injection (Humane Society o the United States,undated). There is also concern over the distressing

side eects o exposure to CO (European Food SaetyAuthority, 2005) while the animal is conscious (Staord,2006) and over the signicant danger to operators. For

these reasons WSPA considers this to be an unacceptablemethod or the euthanasia o dogs and cats.

NOTACCEPTABLE

Nitrous oxide (N20)

This gas is no longer considered appropriate as a soleanaesthetic agent as it does not induce anaesthesia

in animals even at 100% concentrations (Beaver

et al., 2001). I N20 is used on its own it produces

hypoxemia (low oxygen in the blood) (European FoodSaety Authority, 2005) beore respiratory or cardiacarrest (Beaver et al., 2001) and as a result animalsmay become distressed prior to loss o consciousness

(Beaver et al., 2001). This method is consideredinhumane and not acceptable or euthanasia.

NOTACCEPTABLE

Ether

This is a highly infammable volatile liquid, which maybe explosive under some circumstances. It must be

vaporised by the passage o a gas, normally oxygen,to be used as an anaesthetic. Ether is a relatively

dangerous substance to use and causes distress byirritation to the nasal passages and eyes to both theanimal and the operator (Close et al., 1996). This agentis not suitable or euthanasia, because o extreme risk tooperators and the detrimental eects on animal welare.


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Physical methods

Shooting using a ree bullet, penetrating captive bolt,

electrocution, decompression, hanging and drowning


For several reasons physical methods or the euthanasiao dogs and cats are generally not recommended(Close et al., 1997). Some methods are likely to cause

severe pain and suering to animals and are thereoreconsidered inhumane, and unsuitable or euthanasia. Inaddition the high risk o equipment ailure, malunction

and operator error when used in practice will causepain and distress to the animals. The only physicalmethod considered conditionally acceptable by WSPA

shooting with a ree bullet could be used as alast resort in an emergency situation when no other

methods are possible, but not as routine.

Many o these methods may be aestheticallyobjectionable or personnel, making them distressingto perorm and urther increasing the stress that

operators may experience. Furthermore, i operatorsare distressed and dissatised themselves, there is anincreased likelihood o them becoming careless when

handling animals.


Shooting using a ree bullet

An accurate shot to the animals head will resultin immediate destruction o the brain and loss oconsciousness, ollowed by death (Carding, 1977).

However, specialist training and considerable skillis required to ensure that the bullet will penetratethe brain. In addition there is extreme danger to the

operators and any bystanders, and a rearm shouldnever be used in enclosed spaces as there is a risko ricocheting bullets. Moreover, the use o a rearm

is likely to be subject to strict local and nationalregulations. WSPA would only conditionally acceptthis method or use in an emergency situation, when it

is necessary to alleviate the suering o an individualanimal but no acceptable euthanasia methods are

possible, because the animal cannot be handled orgiven pre-euthanasia drugs.

NOTACCEPTABLE

Captive bolt

Although widely used and accepted as a stunningprocedure or the slaughter o large livestock species,this method is generally considered inappropriate ordogs and cats (European Food Saety Authority, 2005).

The penetrative captive bolt pistol must be placed incontact with the animals skull and precise positioningis essential so that the bolt penetrates the correct area

o the brain rst time. Animals must be adequately

restrained so that the head remains steady (Carding,1977; Dennis et al., 1988; Beaver et al., 2001), which

makes this method particularly dicult with earul andaggressive dogs and cats (Carding, 1977). Furthermore,

the conormational dierences between the skulls oindividuals and breeds o dogs increase the risk o amis-stun. The principle skull types are dolichocephalic

(long, narrow head), brachycephalic (short, wide heads)and mesaticephalic (medium proportions).

Use o a captive bolt may be aesthetically unpleasantto the operator, especially as urther measures arenecessary (e.g. pithing or exsanguination) to ensure death

(Beaver et al., 2001). The bleeding that occurs aterpenetration o the skull and ater urther pithing createsa hazard or the operator, due to the risk o coming into

contact with blood and brain matter. This risk may be oparticular concern in rabies-endemic areas.

As there is a high risk o mis-stunning through inadequate

use o the penetrating captive bolt, and hence causingpain and distress, WSPA considers this an unacceptable

method or the euthanasia o dogs and cats.

NOTACCEPTABLE

Electrocution

In theory it is possible to achieve euthanasia byapplying an appropriate electric current and voltagein a two-step process: rst, spanning the animals

brain to render it unconscious producing an eectivestun; second, applying sucient current acrossthe heart to produce cardiac brillation and death

rom hypoxia (Beaver et al., 2001). However, it isWSPAs experience that such ideal conditions arenever achieved in practice. There are grave concerns

over the suitability o the design (Carding, 1977)and maintenance o equipment, which, coupled withlack o training and misuse (Phillips, undated), make

this method inhumane. I an animal is not eectivelystunned, which is oten the case with whole bodyexposure to electric current in electrocution chambers

(Carding, 1977), death results rom cardiac brillationin a conscious animal, and hence involves excruciatingpain and distress. In addition this method may be

extremely hazardous to personnel, and is aestheticallyobjectionable as it causes violent extension and

stiening o the animals limbs, head and neck(Beaver et al., 2001).

WSPA regards electrocution as an unacceptable methodo euthanasia or dogs and cats, as the minimum

conditions necessary or it to be humane are oten notachieved in practice.

NOTACCEPTABLE

Decompression

This method requires the use o decompression

chambers. In theory the low ambient air pressure inthe absence o extra oxygen results in cerebral hypoxia,

leading to loss o consciousness ollowed by death(Carding, 1977). However, expansion o trapped gasesin body cavities leads to adverse physical eects, painand discomort (Close et al., 1996), and is likely tocause anxiety and stress in animals (Close et al., 1997).


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In addition this method may be aesthetically unpleasantor the operator as unconscious animals may bloat,

bleed, vomit, convulse, urinate and deecate duringdecompression (Hatch, 1982).

This method is inhumane and thereore not acceptableor the euthanasia o dogs and cats.

NOTACCEPTABLE

Hanging

Death results by asphyxiation rom constriction o thetrachea ater strangulation, causing the animals earand distress. This method is inhumane and its use is

condemned by WSPA.

NOTACCEPTABLE

Drowning

Prolonged death by asphyxiation ater immersion in

water (drowning) causes animals ear and severe stress(Close et al., 1996). This method is inhumane and itsuse is condemned by WSPA.

Poisons

Strychnine and cyanide


These agents cause excruciating pain and distress to

animals.

NOTACCEPTABLE

Strychnine

Strychnine acts on the nervous system resulting in

painul muscle contractions and violent convulsions.The animal remains conscious and experiences extremepain and distress beore it dies as a result o suocation

(Lumb, 1985; Close et al., 1996; Beaver et al., 2001).This is an unacceptable agent or euthanasia as itsmode o action is inhumane.

NOTACCEPTABLE

Cyanide

Cyanide blocks oxygen uptake, leading to respiratorycollapse. It is accompanied by violent and painul

convulsions prior to the onset o unconsciousness anddeath (Hatch, 1982). In addition, the use o cyaniderepresents an extreme danger to people as they are

equally susceptible to its toxicity. The use o cyanide isinhumane and should never be a method o euthanasia.

The World Society or

the Protection o Animalsfrmly believes that in allsituations when euthanasiais deemed necessary themethods adopted should betruly humane. They shouldachieve rapid, painlessdeath and minimise earand distress to animals. Ourgoal is or all countries to

adopt the humane methodsendorsed by WSPA, and or

this document to be usedto encourage authorities tomake the recommendeddrugs available.


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Staord, K. 2006. Free living dogs. In: The welare o dogs, pp: 3154. Springer,

Dordrecht, The Netherlands.

Wetzel, R.W. and Ramsay, E.C. 1998. Comparison o our r egimens or intraoral

administration o medication to induce sedation in cats prior to euthanasia.Journal

o the American Veterinary Medical Association 213: 243245.

Avariez, J.B. and Caday, L.B. 1958. Magnesium sulphate euthanasia in dogs.

Journal o the American Veterinary Medical Association Aug (15): 213214.

Beaver, B.V., Reed, W., Leary, S., McKiernan, B., Bain, F., Schultz, R., Bennett,

B.T., Pascoe, P., Shull, E., Cork, L.C., Francis-Floyd, R., Amass, K.D., Johnson,

R., Schmidt, R.H., Underwood, W., Thornton, G.W., Kohn, B. 2001. Report o

the AVMA panel on euthanasia.Journal o the American Veterinary Medical

Association 218: 669696.

Bishop, Y. (Ed). 2005. The Veterinary Formulary. Sixth Edition. Pharmaceutical

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Veterinary Association.

Carding, A.H. 1968. Mass euthanasia o dogs and cats with carbon monoxide and/orcarbon dioxide; preliminary trials.Journal o Small Animal Practice 9: 245259.

Carding, T. 1977. Euthanasia o cats and dogs.Animal Regulation Studies 1: 521.

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Close, B., Banister, K., Baumans, V., Bernoth, E.M., Bromage, N., Bunyan, J.,

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Erhart, W., Flecknell, P., Gregory, N., Hackbarth, H., Morton, D., Warwick, C.

1997. Working party r eport: Recommendations or euthanasia o exper imental

animals: Part 2. Laboratory Animals 3: 132.

Dallaire, A. and Chalioux, A. 1985. Premedication o dogs with acepromazine

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Danneman, P.J., Stein, S., Walshaw, S.O. 1997. Humane and practical

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Dennis, M.B., Dong, W.K., Weisbrod, K.A. 1988. Use o captive bolt as a method

o euthanasia or larger laboratory animal species. Laboratory Animal Science 38

(4): 459 462.

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and other scientic purposes. Annex to the EFSA Journal 292: 1136.

Ewbank, R. 1983. Is carbon dioxide euthanasia humane? Nature 305: 268.

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administration o a euthanasia agent in animal shelter cats.Journal o the

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Ames, Iowa State University Press, USA.


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ANNEX

1

ANNEX 1: Dosages and routes o administration o

agents or euthanasia o dogs and cats

The inormation is rom those organisations using drugs or euthanasia

in the eld. The eects o many o these agents are dose dependent. Itis thereore essential that an accurate estimate o the animals weight isobtained prior to euthanasia. In addition the eects o these drugs may

be highly variable and dependent upon the individual animals physicalcharacteristics and circumstances. All manuacturers instructionsshould be consulted and adhered to.

Eutha

nasiaa

gent

Route

ofad

ministr

ation

Dosag

eRe

marks

Us

eofp

re-eut

hanasi

a

drugsind

icated

?

Pentobarbitonesolution

Injectablesolutions suitableor euthanasia(20%: 200mg/

ml)

Intravenous (IV) 150mg/kg or both dogs and cats Best practice

Carcass disposal recommendincineration

Not unlessthe animal isractious

Intraperitoneal(IP)

Proposed dosage schedule is23 x recommended dose or IVadministration when preparationscontaining concentrations o 390mg/ml o Pentobarbitone are used(Sinclair, 2004: p 397.)

120200 mg/kg as necessary(Bishop, 2005:p 291)

Can be an irritant i given by thisroute

Takes longer to take eect than viaIV route: 1530 minutes


Yes, ideallyunless the animalis unconscious,collapsed

Intracardiac (IC) 150mg/kg or both dogs and cats Can be painul i attempted in ullyconscious animals


Yes, this route oadministrationis only suitableor unconscious,collapsed animals

Oraladministration(PO)

Dose or neonatal kittens andpuppies: despite discussion withanimal welare groups we havebeen unable to provide suitableguidance on an acceptable doseor oral administration to neonatesat this time.

Dose or sedation o dogs: 63mg/kg(Ramsay and Wetzel, 1998)

Takes longer to take eect than viaIV route

Powdered preparation delivered in

gelatine capsules can be hiddenin ood and is less likely to bedetected by dogs than mixing theliquid orm with ood.

Highly variable time to take eecteven in dogs given the same dose.

Prolonged time to take eect:3090 minutes.

No

Anaestheticagents given asan overdose.

Thiopentone

Proprool

Intravenous (IV) Given to eect Eective dose is highly variable,dependent upon the animalsage, physical status and use opre-euthanasia drugs

This method is time consumingand costly in comparison to othermethods


Not unlessthe animal isractious, asthese agentsshould be given

intravenously


24/28

24

ANN

EX1

Eutha

nasiaagent

Route

ofad

ministra

tion

Dosag

eRe

marks

Us

eofpre-e

uthana

sia

drugsind

icated?

T61(embutramide,mebezoniumiodine, tetracainehydrochloride)ater sedation

Intravenous (IV) Dogs and cats: 0.3ml/kg Slow, steady rate o injectionrequired

Commercially available as apre-prepared euthanasia solutionaccept in the USA


Yes, shouldbe sedated toensure slowinjection rate

Potassium

chloride (KCl)ater anaesthesia

Intravenous (IV)

or

intracardiac (IC)

One proposed dosage schedule

is 100g o KCI dissolved in 1 litreo water; 2030ml o solutionsucient or euthanasia o dogsweighing 1520kg

12 mmol/kg o body weight willcause cardiac arrest (Beaver etal., 2001)

Oten available commercially as

a powder which is made into aninjectable solution by dissolvingin water

Carcass disposal recommend

incineration

Yes, must be

anaesthetised

Magnesiumsulphate (MgSO4)ater anaesthesia

Intravenous (IV)

or

intracardiac (IC)

Saturated solution o MgSO4. Oneproposed dosage schedule is:

83% solution o MgSO4 dissolvedin boiling water:

Dosage varies little i given byIV or IC route o administration(Avariez and Caday, 1958).

But highly variable dose orindividuals; one suggestedpublished eective dose:

2038 ml or a 15 kg dog (Avariezand Caday, 1958).

80mg/kg dose (Close et al., 1996)

Saturated aqueous solution1g/ml at a dose o2.54.0 mg/kg (Carding, 1977)

Oten available commercially asa powder, which is made into aninjectable solution by dissolvingin water

Saturated solution becomes veryviscous

Large volumes required to achieve

euthanasia


Yes, must beanaesthetised

Gaseousanaestheticse.g. Halothane,Enfurane,

Isofurane,Sevofurane,Desfurane andMethoxyfurane

Inhalation Given to eect

Delivered in a carrier gas (usuallyoxygen) at the minimum alveolarconcentration (MAC)

Only suitable or small animals oranimals already anaesthetised orsurgery

Requires an anaesthetic chamber

or can be delivered via breathingsystems and masks applied tothe ace

Human health hazard i inhaled


Not suitableor use inlarger animalsunless already

anaesthetisedor surgery and,on humanegrounds, theyare not permittedto regainconsciousness


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25

ANNEX

2

ANNEX 2: Guidelines on the intravenous injection o

Pentobarbitone or the euthanasia o dogs and cats

and specialist capture and restraint equipment to prevent

handlers being bitten and to minimise human contact

with animal body uids. To acilitate sae handling o

these animals, sufcient sedation (pages 1314) should

be used prior to injection with the euthanasia agent.

5. Assessment o the animals temperament

and ease o handlingAnimals that are not used to being handled by humans

may experience ear when placed in novel surroundings,which may result in them showing deensive or avoidancebehaviour. Any animals that are likely to be ractious ordicult to handle may pose a risk to personnel through

aggressive behaviour. In these instances it is both morehumane and saer or these animals to be sedated priorto euthanasia with sucient time being allowed or the

sedative to take maximum eect beore euthanasia isundertaken.

Some nervous and aggressive dogs may require muzzlingto avoid danger to handlers. I no muzzle is available,a bandage tied around the dogs nose and then behind

the head (also known as a tape muzzle) can work in theshort term.

Feral cats require special consideration as they aregenerally extremely earul o humans. This presentsboth a welare concern or the cat and a saety concernor the handlers, as the cats deensive-aggressive

behaviour can infict injury. The most satisactorymethod o capturing a eral cat is to use a cat trap with asqueeze back acility (Figure 1). The captured cat is then

pressed against the mesh on the side o the cage so thatan injection o a pre-euthanasia agent (pages 1314) canbe given. Once suitably sedated/immobilised the cat can

be handled saely.

6. Materials

The ollowing materials are required or intravenous

injection:

Syringes

Disposablesyringeswitheccentric(i.e.off-centre)

nozzles. Forcats,asyringesizeof2mlisrecommended.

Fordogs,syringesizesof5,10and20mlwillbe

suitable or most weights.

Disposable needles

Needlediameterismeasuredbythegauge:the

larger the gauge the ner the needle. Needlesareusuallysuppliedindifferentcoloured

containers according to gauge or easy identication.The size o the needle depends upon the size o theanimal and the substance to be injected. For an

Introduction

The World Society or the Protection o Animals stronglyrecommends the use o Pentobarbitone (also sometimescalled Pentobarbitone sodium or sodium pentobarbital);

a barbiturate specically ormulated or euthanasia.The intravenous (IV) injection o Pentobarbitone 20%solution is regarded as the most humane method

o euthanasia or dogs and cats. The method ointravenous injection or dogs and cats can be mastered

easily with training. In most cases animals showlittle or no resistance, provided that they are handledconsiderately and that they are used to close humancontact. In certain countries euthanasia by intravenous

injection may only be perormed by a veterinarian or byoperators working under veterinary supervision.

1. Personnel

Trained, competent and considerate personnel areessential or the humane handling o animals or

euthanasia.

A minimum o two people are required or intravenous

injection: one person should be able to restrain theanimal saely and humanely (reerred to hereater asthe assistant), while the second accurately delivers

the intravenous injection or euthanasia (reerred tohereater as the operator).

2. Preparation

Appropriate preparation must be made or smoothinduction, and to ensure sae and humane handling o

animals or euthanasia. In the rst instance, personnelshould ensure that all materials are available to handand the environment is suitable, as ollows.

3. The environment

A quiet room away rom other animals is required inorder to avoid dogs and cats becoming excited beorethe procedure, which would make them dicult tohandle, requiring additional restraint.

An examination table approximately 90cm in height,with a non-slip surace, acilitates handling and allows

or accurate injection.

Good lighting o the area is essential to enable the

operator to see the site o the injection (usually thecephalic vein on the animals oreleg); thereoreacilitating precise delivery o the injection.

4. Special precautions should be taken orsuspect rabid animalsExtreme care should be taken when handling and

euthanasing animals suspected o having rabies. Special

precautions include protective clothing or personnel,


26/28

26

ANNEX

2

intravenous injection o Pentobarbitone the ollowing

are recommended: Cats: needle o 2224 gauge andlength 0.75 inches (2cm), Dogs: needle o 1822gauge and length 1 inch (2.5 cm) is convenient or

most size o dog.

Cannulae

I permanent plastic cannulae are available or use theyare preerable as they minimise the risk that the needlemay slip during the procedure resulting in some or all o

the drug not being delivered directly into the vein (seesection 7e). The technique or inserting a plastic cannulais similar to that or giving an intravenous injection, but

may take a little more training and practice; insertion isespecially dicult in smaller dogs and cats.

Euthanasia agent

Injection o Pentobarbitone, 20% solution is consideredas best practice; however some euthanasia products

have been combined with a local anaesthetic agentor Phenytoin. The pharmacological dierences are

inconsequential but such compounds may be moreeasily obtained in some countries.

Dose rate

Where possible the animal should be weighed. I this

is not possible, experienced personnel may be able toestimate the animals weight with sucient accuracy.The dose o Pentobarbitone should be determined

according to the manuacturers instructions.

7. Method

(a) Filling the syringe

A new, disposable needle should be attached to thenozzle o a new, disposable syringe, and then inserted

into the bottle containing Pentobarbitone or lling.To prevent a vacuum orming in the bottle, resultingin diculty with subsequent withdrawal o fuid, it isadvisable rst to inject into the bottle an amount o air

equal to the volume o liquid to be withdrawn. Fill the

syringe with the correct dose, calculated according tothe manuacturers instructions or the animals weight.Remove the needle and syringe rom the bottle and

replace the cap on the needle or saety.

(b) Handling and restraint

Dogs

Gently lit the animal on to the examination table. Thedog should be acing the operator who will be giving

the intravenous injection. Large or ractious dogs mayrequire more than one handler or restraint. I theoperator is right handed, the assistant should stand

on the animals let. Where possible the animal shouldbe in the sitting or lying position. The assistants armpasses over the back o the and the other arm holds the

animal under the chin (Figure 2).

Cats

The cat should be gently placed onto the examination

table, acing the operator or intravenous injection. The

assistant should hold the cat against their body, makingthe cat eel secure.

The animals head should be held under its chin withone o the assistants hands, while the other hand

raises the cephalic vein (Figure 3). The cats orelegshould be pushed orward at the elbow, and the thumband orenger used to apply gentle tourniquet pressure,

as described or dogs in Figure 4.

(c) Site o injection

The cephalic vein in the animals oreleg is the mostconvenient site or intravenous injection. When theanimal is held correctly the cephalic vein is visible

on top o the oreleg (Figure 4). Once the animal hasbeen suitably restrained, it may be necessary to aidvisualisation o the vein, particularly in cats and small

dogs, to clip a small amount o hair on the orelegwhere the injection is to be given.

Figure 1.

Photograph o a squeeze-back cage or use with

methods for the euthanasia of dogs and cats- english.pdf

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